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排序方式： 共有1065条查询结果，搜索用时 15 毫秒
1.
彭国瑞 《冶金标准化与质量》2005,43(5):3-4
采用x射线荧光光谱仪测定GH4169合金中的锰、硅、镍、铬、钼、铝、钛、铌。研究了测量条件及基体 吸收—增强效应的校正。还时测量精度进行了研究,各元素的相对标准偏差分别为0．0466％～O．6777％。与 化学分析结果对照结果良好。 相似文献
2.
《Materials and Manufacturing Processes》2012,27(7-8):793-797
The creep properties of as-cast Ti-48Al-2Cr (at%) alloy which had been strengthen with addition of 2 at% Cr were investigated. Tensile creep experiments were performed in air at temperatures from 600–800°C and initial stresses ranging from 150 to 180 MPa. Stress exponent and activation energy were both measured. Data indicates that the alloy exhibits steady state creep behavior and the steady state creep rate is found to depend on the applied load and temperature. The measured power law stress exponent for steady state creep rate is found to be close to 3 and the apparent activation energy for creep is calculated to be 15.7 kJ/mol. The creep resistance of the present alloy was also compared with binary Ti-48Al (at%) to evaluate the effect of Cr addition on creep resistance of TiAl. It is concluded that addition of 2 at% of Cr does not have significant effect on the creep resistance of TiAl. 相似文献
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以国产蒸汽发生器传热管用GH690合金为研究对象,通过评价其断裂韧性及拉伸特性,结合光学显微镜、扫描电镜和透射电镜分析,研究了合金由室温-623K的力学性能.研究结果表明,室温下GH690合金低的层错能,易生成形变孪晶,使得合金在孪生的协调下塑性变形能力提高,同时孪晶促进裂纹扩展转向,使合金在断裂过程中吸收更多的能量,维持合金高的断裂韧性.随着温度的升高,合金的层错能增加,导致形变孪晶生成困难,合金应力集中程度加剧,裂纹从而平直扩展,合金的断裂韧性降低.由于合金的室温层错能较低,合金在拉伸时能够通过孪生协调变形,同时生成的孪晶阻碍了位错的滑移而提高了合金的强度和塑性.随着形变温度的升高,合金通过孪生协调变形的能力降低,导至合金的变形机制由孪生转变为滑移,滑移产生的加工硬化效应小于孪生,故合金的强度和延伸率随之降低. 相似文献
5.
The corrosion behavior of engine materials of airplanes working in marine environments is accelerated by the synergistic effects of NaCl particles and water vapor at high temperatures. This work examined the corrosion behavior of GH4169 alloy with a NaCl solution spraying at 600 degrees C using an oxidation kinetics test and micro characterization technology in the aspects of corrosion kinetics, corrosion layer phase composition, and microstructure. The weight gain of the GH4169 alloy corroded in the NaCl solution spraying environment was much lower than that in solid NaCl + wet O-2 after 20 h corrosion at 600 degrees C. The corrosion products of the GH4169 alloy in the NaCl solution spray environment were less complex than those in the solid NaCl + wet O-2 environment, but they were denser. In addition, Cl was concentrated in the inner layer of the corrosion products and accelerated the corrosion of GH4169 alloy via an active oxidation mechanism at the initial stage. When NaCl deposition was increased, the corrosion mechanism of GH4169 alloy changed gradually to Cl-induced active oxidation. The sensitivity of GH4169 alloy in the NaCl solution spray environment at 600 degrees C was analyzed. Overall, the sensitivity of elements in GH4169 alloy to chlorine activated corrosion was Ti > Al > Nb, Cr > Fe > Mo, Ni, whereas the sensitivity of the oxides was TiO2 > MoO2 > Cr2O3(Nb2O5) > Fe2O3 > Al2O3 > NiO. 相似文献
6.
GH4065合金使用期间较易出现各种损伤,为此预制了具有合适开口角度的V型,通过激光增材制造工艺对损伤区进行修复,测试分析不同开口V型角度条件下试样的显微组织结构、成形质量、表面硬度及其力学特性.研究结果表明,所有开口V型下形成了基本一致的修复区域组织,呈现外延生长特征,侧壁枝晶保持与侧壁垂直的方向生长.由熔覆层逐渐过... 相似文献
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8.
Kai P. Leschonski Svend G. Kaasgaard Nikolaj Spodsberg Kristian B. R. M. Krogh Mirjam A. Kabel 《International journal of molecular sciences》2022,23(22)
Fungal arabinofuranosidases (ABFs) catalyze the hydrolysis of arabinosyl substituents (Ara) and are key in the interplay with other glycosyl hydrolases to saccharify arabinoxylans (AXs). Most characterized ABFs belong to GH51 and GH62 and are known to hydrolyze the linkage of α-(1→2)-Ara and α-(1→3)-Ara in monosubstituted xylosyl residues (Xyl) (ABF-m2,3). Nevertheless, in AX a substantial number of Xyls have two Aras (i.e., disubstituted), which are unaffected by ABFs from GH51 and GH62. To date, only two fungal enzymes have been identified (in GH43_36) that specifically release the α-(1→3)-Ara from disubstituted Xyls (ABF-d3). In our research, phylogenetic analysis of available GH43_36 sequences revealed two major clades (GH43_36a and GH43_36b) with an expected substrate specificity difference. The characterized fungal ABF-d3 enzymes aligned with GH43_36a, including the GH43_36 from Humicola insolens (HiABF43_36a). Hereto, the first fungal GH43_36b (from Talaromyces pinophilus) was cloned, purified, and characterized (TpABF43_36b). Surprisingly, TpABF43_36b was found to be active as ABF-m2,3, albeit with a relatively low rate compared to other ABFs tested, and showed minor xylanase activity. Novel specificities were also discovered for the HiABF43_36a, as it also released α-(1→2)-Ara from a disubstitution on the non-reducing end of an arabinoxylooligosaccharide (AXOS), and it was active to a lesser extent as an ABF-m2,3 towards AXOS when the Ara was on the second xylosyl from the non-reducing end. In essence, this work adds new insights into the biorefinery of agricultural residues. 相似文献
9.
Marc De Doncker Chloé De Graeve Dr. Jorick Franceus Dr. Koen Beerens Prof. Vladimír Křen Dr. Helena Pelantová Dr. Ronny Vercauteren Prof. Dr. Tom Desmet 《Chembiochem : a European journal of chemical biology》2021,22(23):3319-3325
The substantial increase in DNA sequencing efforts has led to a rapid expansion of available sequences in glycoside hydrolase families. The ever-increasing sequence space presents considerable opportunities for the search for enzymes with novel functionalities. In this work, the sequence-function space of glycoside hydrolase family 94 (GH94) was explored in detail, using a combined approach of phylogenetic analysis and sequence similarity networks. The identification and experimental screening of unknown clusters led to the discovery of an enzyme from the soil bacterium Paenibacillus polymyxa that acts as a 4-O-β-d -glucosyl-d -galactose phosphorylase (GGalP), a specificity that has not been reported to date. Detailed characterization of GGalP revealed that its kinetic parameters were consistent with those of other known phosphorylases. Furthermore, the enzyme could be used for production of the rare disaccharides 4-O-β-d -glucosyl-d -galactose and 4-O-β-d -glucosyl-l -arabinose. Our current work highlights the power of rational sequence space exploration in the search for novel enzyme specificities, as well as the potential of phosphorylases for rare disaccharide synthesis. 相似文献
10.
采用自行设计测定塑性收缩的方法,对不同胶凝材料净浆在不同水胶比情况下的塑性收缩变化规律及矿物掺和料对塑性收缩的影响进行了研究。试验结果表明,净浆塑性收缩与水胶比有关;水胶比为0.28~0.35时,塑性收缩随水胶比的增加而减小,而在0.35~0.45范围内随水胶比的增加而增加;矿物掺和料的品种及掺量对净浆的塑性收缩也有很大的影响。 相似文献